body {
    nav {
        width: 1000px;
        height: 60px;
        margin: 20px auto;
        background-color: white;
        padding: 20px;
        display: flex;
        align-items: center;
        justify-content: space-between;
        .left {
            width: 100px;
            height: 100%;
            display: flex;
            justify-content: space-between;
            align-items: center;
            .arrow {
                width: 15px;
                height: 15px;
                border-bottom: 2px solid black;
                border-left: 2px solid black;
                transform: rotate(45deg);
            }
            span {
                font-size: 14px;
            }
        }
        .center {
            font-size: 20px;
        }
        select {
            outline: none;
            border-radius: 5px;
            width: 100px;
            height: 30px;
            background-color: rgba(0, 153, 51, 1);

            box-shadow: none;
            font-size: 14px;
            color: #ffffff;
            option {
                background-color: rgb(221, 218, 218);
                color: #666;
            }
        }
    }
    main {
        width: 1000px;
        display: flex;
        flex-wrap: wrap;

        margin: 0 auto;
        > .box {
            margin-right: 15px;
            margin-left: 16px;
            margin-bottom: 30px;
            width: 300px;
            background-color: white;
            border-top-right-radius: 10px;
            border-top-left-radius: 10px;
            .title {
                width: 100%;
                height: 40px;
                line-height: 40px;
                color: #333;
                font-size: 15px;
                border-bottom: 1px solid rgb(214, 214, 214);
                padding-left: 15px;
                padding-right: 15px;
                span {
                    font-size: 14px;
                    color: #666;
                    &:nth-child(2){
                        color: red;
                    }
                }
            }
            .join{
                width: 100%;
                height: 40px;
                background-color: green;
                color: white;
                border: 0px;
            }
            .joinin{
                width: 100%;
                height: 40px;
                background-color: rgba(204, 204, 204, 1);
                color: white;
                border: 0px;
            }
        }
    }
}
